The present invention relates to steering equipment for work vehicles, and more particularly, to a control device for engaging a steering operating unit, such as a fast steering system for agricultural vehicles.
Known steering units used in agricultural vehicles usually include a steering column having a longitudinal axis, a steering transmission shaft mounted inside the steering column for rotating about the longitudinal axis and a steering wheel mounted on the steering transmission shaft. Additionally, a control device for actuating an operating unit may be provided. The control device may be operable to induce conversion between a “conventional steering mode” and a “fast steering mode” as described in EP-A-1.142.773, now U.S. Published Patent Application No. 2001/0032461 A1.
Generally, the control device is mounted on the steering column and usually includes a reference member, which can move along the longitudinal axis of the steering column. An actuating member is provided which can be operated by the vehicle operator for displacing the reference member along the longitudinal axis. A sensor is provided to detect the position of the reference member along the longitudinal axis. Finally, a connecting mechanism, either mechanical or electrical, is provided for connecting the sensor to the reference member.
The steering unit is designed to control the steering of a pair of wheels of the vehicle, usually by means of a hydraulic steering circuit. The steering circuit enables the steering wheel to rotate about the longitudinal axis even when the wheels have reached their maximum steering angle. Thus, the steering wheel may continue to make an indefinite number of complete rotations, even after full steering lock has been reached.
As a result of this unrestricted rotation of the steering wheel, steering equipment of the above type presents the problem that an actuator for activating another function (such as the “fast steering mode”) cannot be readily affixed to the steering wheel for rotation therewith, since the connecting mechanism between the sensor and the reference member could be damaged or become inoperable due to the indefinite or unrestricted steering wheel rotations. Instead, the actuator is connected in a slidable manner to the is steering column underneath the steering wheel. This poses the additional problem of finding an ergonomic position, which is not hidden by the steering wheel.
The problems and drawbacks described above are partially overcome by mounting the actuator on the dashboard of the vehicle, separate from the steering column. In this configuration, however, the vehicle operator must let go of the steering wheel with at least one hand to operate the actuator, which is not recommendable from an ergonomic point of view.
Thus, the purpose of the present invention is to provide steering equipment for work vehicles that overcomes the problems and drawbacks referred to above.